Understanding insecticide resistance

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When you find something that works, the instinct is to stick with it. However, when it comes to pesticides, overuse of favorite products leads to the development of insecticide resistance. 

Resistance is a change in the susceptibility of some insects or mites in an arthropod pest population to an insecticide. This change allows them to survive insecticide applications that previously controlled them and subsequently pass the resistance traits to the next generation.

To reduce the risk of resistance, it is important to rotate pesticides – not by brand or trade name, but by active ingredients and modes of action.

Understanding mode-of-action classification

The Insecticide Resistance Action Committee (IRAC) groups pesticides by mode of action (MOA). Different chemical classes can have similar modes of action and are listed as subgroups. Rotating insecticides based on MOA reduces the chance of resistance developing. The modes of action of insecticides and miticides are numbered, color coded and available on the IRAC website. In addition, the IRAC group number or numbers are listed on the product label of every insecticide. The chart below details commonly used insecticides, their active ingredients and their respective IRAC groups.

To minimize the risk of pest populations developing resistance, follow these guidelines:

  • Monitor pests. Scout crops to determine if population levels meet economic thresholds and target the most susceptible life stage(s) of an insect. Continue to monitor after applications to assess efficacy and monitor for signs of resistance.
  • Select and use pesticides judiciously. Properly identify insects and choose an insecticide that is active on the target pest.
  • Apply according to label instructions. Make sure equipment is properly calibrated and apply at labeled rate. Follow label directions regarding treatment intervals and maximum applications per year.
  • Rotate insecticides. If repeated applications are necessary, rotate insecticides between IRAC groups. Do not make more than two consecutive applications of insecticides with the same mode of action before rotating.
  • Keep good records. Track which insect species were present, and when and where applications were made. Record the rate, timing and number of applications made. Be sure to track the level of control achieved. Use these records to aid in planning for future applications.

Strictly adhering to insecticide resistance management practices can help reduce the chance of resistance developing in the first place.

XXpire is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. State restrictions on the sale and use of Entrust and Intrepid apply. Consult the label before purchase or use for full details. Always read and follow label directions.


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